/Engine/Source/Runtime/Core/Public/Math/UnrealMathUtility.h
Calculates whether a Point is within a cone segment, and also what percentage within the cone (100% is along the center line, whereas 0% is along the edge)
true if the point is within the cone, false otherwise.
static bool GetDistanceWithinConeSegment ( FVector Point, FVector ConeStartPoint, FVector ConeLine, float RadiusAtStart, float RadiusAtEnd, float & PercentageOut )